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Relativistic jet
:The lower-energy non-relativistic version of this phenomenon is described at polar jet. where the relativistic plasma is collimated into jets which escape along the pole of the supermassive black hole]] Relativistic jets are extremely powerful jets of plasma which emerge from the centers of some active galaxies, notably radio galaxies and quasars. Their lengths can reach several thousandBiretta, J. (1999, January 6). Hubble Detects Faster-Than-Light Motion in Galaxy M87 (http://www.stsci.edu/ftp/science/m87/m87.html) or even hundreds of thousands of light years.Yale University - Office of Public Affairs (2006, June 20). Evidence for Ultra-Energetic Particles in Jet from Black Hole (http://www.yale.edu/opa/newsr/06-06-20-01.all.html) It is believed that the twisting of magnetic fields in the accretion disk collimates the outflow along the rotation axis of the central object, so that when conditions are suitable, a jet will emerge from each face of the accretion disk. If the jet is oriented along the line of sight to earth, relativistic beaming will change its apparent brightness. The mechanisms for the creation of jetsMeier, L. M. (2003). The Theory and Simulation of Relativistic Jet Formation: Towards a Unified Model For Micro- and Macroquasars, 2003, New Astron. Rev. '', '''47', 667. (http://arxiv.org/abs/astro-ph/0312048) and the composition of jets Georganopoulos, M.; Kazanas, D.; Perlman, E.; Stecker, F. (2005) Bulk Comptonization of the Cosmic Microwave Background by Extragalactic Jets as a Probe of their Matter Content, The Astrophysical Journal '', '''625', 656. (http://arxiv.org/abs/astro-ph/0502201) are still a matter of much debate in the scientific community. It is believed that the jets are composed of an electrically neutral mixture of electrons, positrons and protons in some proportion. emitting a relativistic jet, as seen by Hubble Space Telescope's WFPC2 in the visible spectrum.]] Similar jets, though on a much smaller scale, can develop around the accretion disks of neutron stars and stellar black holes. These systems are often called microquasars. A famous example is SS433, whose well-observed jet has a velocity of 0.23c, although other microquasars appear to have much higher (but less well measured) jet velocities. Even weaker and less-relativistic jets may be associated with many binary systems; the acceleration mechanism for these jets may be similar to the magnetic reconnection processes observed in the Earth's magnetosphere and the solar wind. It is believed that the formation of relativistic jets is the key to explaining the production of gamma-ray bursts. These jets have Lorentz factors of ~ 100, making them one of the fastest celestial objects currently known. Rotating black hole as energy source Because of the enormous amount of energy needed to launch a relativistic jet, some jets are thought to be powered by spinning black holes. There are two competing theories for how the energy is transferred from the black hole to the jet. * Blandford-Znajek process.Blandford, R. D., Znajek, R. L. (1977), Monthly Notices of the Royal Astronomical Society, 179, 433 This is the most commonly agreed theory for the extraction of energy from the central black hole. The magnetic fields around the accretion disk are dragged by the spin of the black hole. The relativistic material is possibly launched by the tightening of the field lines. * Penrose mechanism.Penrose, R. (1969). Gravitational collapse: The role of general relativity. Nuovo Cimento Rivista, Numero Speciale 1', 252-276. This extracts energy from a rotating black hole by frame dragging. This theory was later proven to be able to extract relativistic particle energy,Williams, R. K. (1995, May 15). Extracting x rays, Ύ rays, and relativistic e-e+ pairs from supermassive Kerr black holes using the Penrose mechanism. ''Physical Review, '''51(10), 5387-5427. and subsequently shown to be a possible mechanism for the formation of jets.Williams, R. K. (2004, August 20). Collimated escaping vortical polar e-e+ jets intrinsically produced by rotating black holes and Penrose processes. The Astrophysical Journal, 611, 952-963. (http://arxiv.org/abs/astro-ph/0404135) Other images Image:NGC_5128.jpg|Centaurus A in x-rays showing the relativistic jet Image:M87 jet radio.jpg|The M87 jet seen by the Very Large Array in radio frequency (the viewing field is larger and rotated with respect to the above image). See also *Bipolar outflow Further reading *Melia, Fulvio, The Edge of Infinity. Supermassive Black Holes in the Universe 2003, Cambridge University Press, ISBN 978-0-521-81405-8 (Cloth) References Category:Astrophysics Category:Jet